The present invention relates to a light-weight, flexible wave absorber which is used for evaluation of electromagnetic wave radiation characteristics of an electronic device or for prevention or suppression of electromagnetic interference in the electronic device. More particularly, the present invention concerns a wave absorber which is characterized in that primary particles of composite carbon black particles are dispersed into an insulating matrix.
As the number of apparatuses based on electronics increases, troubles caused by electromagnetic noise generated from these apparatuses have been recently increasingly reported. An RF anechoic box for use in accurate evaluation of electromagnetic waves emitted from these apparatuses or for the purpose of attenuating unnecessary electromagnetic waves radiated from electronic apparatuses, an electromagnetic absorption panel has been developed.
Well known examples include a ferrite tile which has a radio wave absorptivity and is provided on a wall of a high-rise building for the purpose of TV ghost phenomenon prevention. There has also been developed a radio wave absorbing board for the purpose of suppressing an error in a radio LAN for radio data transfer in a room or of avoiding wiretapping. Further as an RF anechoic room for evaluation of radio waves emitted from a radio apparatus, there has been used a radio wave absorber which is made of carbon black impregnated into foamed urethane.
However, such ferrite tile or radio wave absorbing board can be applied only to building materials or the like, because it is large in specific gravity and cannot be bent. Such radio wave absorbing panel, that is made of ferrite or carbonyl iron dispersed into rubber synthetic resin, is problematic in that a lot of ferrite and carbonyl iron is filled into the rubber of synthetic resin as a base material because of its large specific gravity. Therefore, the panel tends to be very fragile, so the panel cannot be used for a curved surface or interior of an electronic apparatus.
A tile made of carbon black dispersed into rubber or synthetic resin is lighter in weight and more flexible than a tile made of ferrite or carbonyl iron dispersed into rubber or synthetic resin. However, the former tile has an operable frequency band having a central X band (of 8 to 12.5 GHz). For this reason, when the aforementioned tile is employed for mobile communication devices which have been rapidly popular in these years, it fails, in current circumstances, to provide sufficient characteristics for the devices employing their L (1 to 2 GHz) or S (2 to 4 GHz) band.